Method for reporting system information in wireless communication and apparatus for supporting same

ABSTRACT

A method for a terminal reporting system information in a wireless communication system is disclosed. The method comprises: receiving a system information report request of a neighboring cell from a serving cell; deciding whether to report the system information on the neighboring cell, which is obtained in advance, to the serving cell; and reporting the system information that is obtained in advance to the serving cell when a decision is made to report the system information, wherein the system information that is obtained in advance is system information of the neighboring cell that is obtained before receiving the system information report request.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method for reporting system information by auser equipment (UE) in a wireless communication system and an apparatusfor supporting the same.

2. Related Art

3^(rd) generation partnership project (3GPP) long term evolution (LTE)which is improvement of a universal mobile telecommunications system(UMTS) is introduced as 3GPP release 8. The 3GPP LTE uses orthogonalfrequency division multiple access (OFDMA) in a downlink and uses singlecarrier-frequency division multiple access (SC-FDMA) in an uplink.Multiple input multiple output (MIMO) having maximum four antennas areadopted. In recent years, 3GPP LTE-advanced (LTE-A) which is anevolution of the 3GPP LTE has been discussed.

A closed subscriber group (CSG) allows a limited access for only aspecific subscriber to be introduced to provide a service having higherquality. A base station that can provide a CSG service may be homeeNodeB (HNB) and a cell providing an authorized service to CSGsubscribers may be a CSG cell. In the 3GPP, a basic requirement of theCSG is disclosed in 3GPP TS 22.220 V1.0.1 (2008-12) “Servicerequirements for Home NodeBs and Home eNodeBs (Release 9)”.

A feature of a CSG cell limitatively providing the service isillustrated even in handover to the CSG cell. Whether a user equipment(UE) is a CSG member of a corresponding cell may be problematic inperforming the handover to the CSG cell. As a result, the handover tothe CSG cell may be implemented by a first step in which the UE reportsa cell measurement result and a second step in which the UE acquiressystem information from a target cell and reports the acquired systeminformation to a service cell.

When a UE receives a message indicating that system information of aneighboring cell will be reported from a serving cell, the UE acquiresthe system information by accessing the neighboring cell. The acquiredsystem information is transmitted to the serving cell. While the UEaccesses the neighboring cell in order to acquire the systeminformation, the serving cell cannot transmit any command/message/datato the UE.

Meanwhile, the UE may acquire system information regarding theneighboring cell in advance before being instructed with reporting thesystem information from the serving cell. Even in such a case, the UEmay perform accessing the neighboring cell by leaving the serving cellin order to newly acquire the system information regarding theneighboring cell as an unnecessary step in some cases. Therefore, a moreefficient system information reporting method of the UE is required.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for reportingperformed by a in a wireless communication system and an apparatus forsupporting the same.

In an aspect, a method for reporting system information by a UE in awireless communication system is provided. The method includes receivinga system information reporting request of a neighboring cell from aserving cell, determining whether to report to the serving cell systeminformation of the neighboring cell acquired in advance, and reportingto the serving cell the system information of the neighboring acquiredin advance when it is determined to report. The system information ofthe neighboring cell acquired in advance is system information of theneighboring cell which is acquired before receiving the systeminformation reporting request.

The step of determining whether to report the system information of theneighboring cell acquired in advance may include determining to reportto the serving cell the system information of the neighboring cellacquired in advance, when the UE has the system information of theneighboring cell acquired in advance.

The method may further include transmitting to the serving cell controlinformation regarding the system information of the neighboring cellacquired in advance together with the system information of theneighboring cell acquired in advance.

The control information may include an indicator indicating that thesystem information of the neighboring cell acquired in advance is thesystem information of the neighboring cell acquired before receiving asystem information reporting request message.

The control information may further include an indicator indicating thetime when the system information of the neighboring cell acquired inadvance is acquired.

The method may further include receiving from the serving cell aready-acquired system information report indicator indicating whetherreporting the system information of the neighboring cell acquired inadvance is allowed.

The step of determining whether to report to the serving cell the systeminformation of the neighboring cell acquired in advance may includedetermining to report to the serving cell the system information of theneighboring cell acquired in advance, if the ready-acquired systeminformation report indicator indicates that the reporting the systeminformation is allowed and the UE has the system information of theneighboring cell acquired in advance.

The method may further include transmitting to the serving cell controlinformation regarding the system information of the neighboring cellacquired in advance together with the system information of theneighboring cell acquired in advance.

The control information may further include an indicator indicating thetime when the system information of the neighboring cell acquired inadvance is acquired.

The method may further include, when it is determined not to report thesystem information, acquiring the system information from theneighboring cell and transmitting the acquired system information to theserving cell.

In another aspect, a UE that operates in a wireless communication systemis provided. The UE include a radio frequency (RF) unit transmitting orreceiving a radio signal and a processor operably coupled to the RFunit. The processor is configured for receiving a system informationreporting request of a neighboring cell from a serving cell, determiningwhether to report to the serving cell system information of theneighboring cell acquired in advance, and reporting to the serving cellthe system information of the neighboring acquired in advance when it isdetermined to report. The system information of the neighboring cellacquired in advance is system information of the neighboring cell whichis acquired before receiving the system information reporting request.

Through a method for reporting system information according to anembodiment of the present invention, a time used for a UE to reportsystem information of a neighboring cell to a serving cell can bedecreased. Therefore, a handover delay of a handover procedure requiringsystem information of a target cell can be decreased. Further, aprocedure in which the UE unnecessarily receives the system informationof the neighboring cell is skipped, and as a result, a time when theserving cell loses controllability of the UE can be decreased.Therefore, mobility increased by the UE can be more efficientlysupported and efficiency of traffic processing between the UE and a cellcan be increased, thereby improving processing rate of an entire system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system according to thepresent invention.

FIG. 2 is a block diagram illustrating a radio protocol architecture fora user plane.

FIG. 3 is a block diagram illustrating a radio protocol architecture fora control plane.

FIG. 4 is a flowchart illustrating an operation of a UE in an RRC idlestate.

FIG. 5 is a flowchart illustrating a process of establishing an RRCconnection.

FIG. 6 is a flowchart illustrating a process of reconfiguring the RRCconnection.

FIG. 7 is an exemplary diagram illustrating a radio link failure.

FIG. 8 is a flowchart illustrating a success in a process ofreestablishing a connection.

FIG. 9 is a flowchart illustrating a failure in the process ofreestablishing the connection.

FIG. 10 is a flowchart illustrating the existing measurement performingmethod.

FIG. 11 illustrates one example of a measurement configurationconfigured for the UE.

FIG. 12 illustrates an example of deleting a measurement identity.

FIG. 13 illustrates an example of deleting a measurement object.

FIG. 14 is a diagram illustrating one example of a wirelesscommunication system illustrating a HeNB operation.

FIG. 15 exemplifies a CSG scenario.

FIG. 16 exemplifies a pico scenario.

FIG. 17 is a flowchart illustrating an operation of a UE that performsthe method for reporting system information according to an embodimentof the present invention.

FIG. 18 is a flowchart illustrating one example of a method forreporting system information according to an embodiment of the presentinvention.

FIG. 19 illustrates an operating flowchart of a UE that performs themethod for reporting system information according to an embodiment ofthe present invention.

FIG. 20 is a flowchart illustrating one example of a method forreporting system information according to an embodiment of the presentinvention.

FIG. 21 is a diagram illustrating another example of the method forreporting system information according to an embodiment of the presentinvention.

FIG. 22 is a block diagram illustrating a wireless apparatus which maybe implemented by the embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 illustrates a wireless communication system according to thepresent invention. The wireless communication system may also be calledan evolved-UMTS terrestrial radio access network (E-UTRAN) or a longterm evolution (LTE)/LTE-A system.

The E-UTRAN includes a base station (BS) 20 that provides a controlplane and a user plane to a user equipment (UE) 10. The UE 10 may befixed or movable and may be called other terms such as a mobile station(MS), a user terminal (UT), a subscriber station (SS), a mobile terminal(MT), a wireless device, and the like. The base station 20 represents afixed station that communicates with the UE 10, and may be called otherterms such as an evolved-NodeB (eNB), a base transceiver system (BTS),an access point, and the like.

The base stations 20 may be connected to each other through an X2interface. The base station 20 is connected with an evolved packet core(EPC) 30 through an S1 interface, in more detail, a mobility managemententity (MME) through an S1 MME and a serving gateway (S-GW) through anSI-U.

The EPC 30 is constituted the MME, the S-GW, and a packet data networkgateway (P-GW). The MME has access information of the UE or informationon a capability of the UE, and the information is primarily used formobility management of the UE. The S-GW is a gateway having the E-UTRANas an end point and the P-GW is a gateway having a PDN as the end point.

Layers of a radio interface protocol between the UE and a network may bedivided into an L1 (first layer), an L2 (second layer), and an L3 (thirdlayer) based three lower layers of an open system interconnection (OSI)reference model which is widely known in a communication system andamong them, a physical layer that belongs to the first layer provides aninformation transfer service using a physical channel and a radioresource control (RRC) layer positioned on the third layer serves tocontrol radio resources between the UE and the network. To this end, theRRC layer exchanges an RRC message between the UE and the base station.

FIG. 2 is a block diagram illustrating a radio protocol architecture fora user plane. FIG. 3 is a block diagram illustrating a radio protocolarchitecture for a control plane. A data plane is a protocol stack foruser data transmission and the control plane is a protocol stack fortransmitting a control signal.

Referring to FIGS. 2 and 3, a physical (PHY) layer provides theinformation transfer service to an upper layer by using the physicalchannel. The physical layer is connected with a medium access control(MAC) layer as an upper layer through a transport channel. Data movebetween the MAC layer and the physical layer through the transportchannel. The transport channel is classified depending on a transmissionmethod and a transmission feature through a radio interface.

Data move between different physical layers, that is, between physicallayers of a transmitter and a receiver through the physical channel. Thephysical channel may be modulated by orthogonal frequency divisionmultiplexing (OFDM) and uses a time and a frequency as the radioresource.

A function of the MAC layer includes mapping between a logic channel andthe transport channel, and multiplexing/demultiplexing to a transportblock provided to the physical channel onto the transport channel of anMAC service data unit (SDU) that belongs to the logic channel. The MAClayer provides a service to a radio link control (RLC) layer through thelogic channel.

A function of the RLC layer includes concatenation, segmentation, andreassembly of an RLC SDU. In order to assure various quality of services(QoS) requested by a radio bearer (RB), the RLC layer provides threeoperating modes of a transparent mode (TM), an unacknowledged mode (UM),and an acknowledged mode (AM). An AM RLC provides error correctionthrough an automatic repeat request (ARQ).

A function of a packet data convergence protocol (PDCP) layer on theuser plane includes transferring of user data, header compression, andciphering. A function of a packet data convergence protocol (PDCP) layeron the user plane includes transferring of control plane data andciphering/integrity protection.

The radio resource control (RRC) layer is defined only on the controlplane. The RRC layer serves to control the logic channel, the transportchannel and the physical channels in association with configuration,re-configuration, and release of radio bearers. The RB means a logicroute provided by the first layer (PHY layer) and the second layers (theMAC layer, the RLC layer, and the PDCP layer) in order to transfer databetween the UE and the network.

Setting the RB defines features of the radio protocol layer and channelin order to provide a specific service and means a process of settingrespective detailed parameters and operating methods. The RB may bere-divided into two types of a signaling RB (SRB) and a data RB (DRB).The SRB is used as a passage for transmitting the RRC message on thecontrol plane and the DRB is used as a passage for transmitting the userdata on the user plane.

When an RRC connection is established between the RRC layer of the UEand the RRC layer of the E-UTRAN, the UE is in an RRC connected stateand if not, the UE is in an RRC idle state.

A downlink transport channel for transmitting data from the network tothe UE includes a broadcast channel (BCH) for transmitting systeminformation and besides, the downlink transport channel includes adownlink shared channel (SCH) for transmitting user traffic or a controlmessage. Traffic or a control message of a downlink multicast orbroadcast service may be transported through the downlink SCH ortransported through an additional downlink multicast channel (MCH).Meanwhile, an uplink transport channel for transporting data from the UEto the network includes a random access channel (RACH) for transportingan initial control message and besides, an uplink shared channel (SCH)for transporting the user traffic or control message.

The logical channel that is positioned on the transport channel andmapped to the transport channel includes a broadcast control channel(BCCH), a paging control channel (PCCH), a common control channel(CCCH), a multicast control channel (MCCH), a multicast traffic channel(MTCH), and the like.

The physical channel is constituted by a plurality of OFDM symbols in atime domain and a plurality of sub-carriers in a frequency domain. Onesub-frame is constituted by the plurality of OFDM symbols in the timedomain. A resource block as a resource allocation unit is constituted bythe plurality of OFDM symbols and the plurality of sub-carriers.Further, each sub-frame may use specific sub-carriers of specific OFDMsymbols (e.g., a first OFDM symbol) of a corresponding sub-frame for thephysical downlink control channel (PDCCH), that is, an L1/L2 controlchannel. A transmission time interval (TTI) is a unit time oftransmitting the sub-frame.

Hereinafter, the RRC state and the RRC connection method of the UE willbe described in detail.

The RRC state represents whether the RRC layer of the UE is logicallyconnected with the RRC layer of the E-UTRAN and a case in which both RRClayers are logically connected to each other is called the RRCconnection state and a case in which both RRC layers are not logicallyconnected to each other is called the RRC idle state. Since the RRCconnection exists in the UE in the RRC connection state, the E-UTRAN maydetermine the existence of the corresponding UE by the unit of a cell tothereby effectively control the UE. On the contrary, the E-UTRAN may notdetermine the UE in the RRC idle state and a core network (CN) ismanaged by the unit of a tracking area which a region unit larger thanthe cell. That is, it is determined whether the UE in the RRC idle stateexists by the unit of a large region, and the UE needs to move to theRRC connection state in order to receive a general mobile communicationservice such as voice or data.

When a user first turns on a power supply of the UE, the UE firstretrieves an appropriate and thereafter, the UE stays in the RRC idlestate in the corresponding cell. The UE in the RRC idle stateestablishes the RRC connection with the E-UTRAN through an RRCconnection procedure at least when the UE in the RRC idle state needs tomake the RRC connection, and is transited to the RRC connections state.Cases in which the UE in the RRC idle state needs to make the RRCconnection are various, and for example, uplink data transmission isrequired due to a user's call attempt or when a paging message isreceived from the E-UTRAN, the cases may include response messagetransmission thereto.

A non-access stratum layer located above the RRC layer performsfunctions such as session management and mobility management.

In order to manage mobility of the UE on the NAS layer, two states ofEPS mobility management (EMM)-REGISTERED and EMM-DEREGISTERED aredefined and both states are applied to the UE and the MME. An initial UEis in the EMM-DEREGISTERED state and the UE performs a process ofregistering the initial UE in a corresponding network through an initialattach procedure in order to access the network. When the attachprocedure is successfully performed, the UE and the MME are in theEMM-REGISTERED state.

In order to manage a signaling connection between the UE and the EPC,two states of an EPS connection management (ECM)-IDLE state and anECM-CONNECTED state are defined and both states are applied to the UEand the MME. When the UE in the ECM-IDLE state makes the RRC connectionwith the E-UTRAN, the corresponding UE is in the ECM-CONNECTED state.When the MME in the ECM-IDLE state makes an S1 connection with theE-UTRAN, the MME is in the ECM-CONNECTED state. When the UE is in theECM-IDLE state, the E-UTRAN does not have context information of the UE.Therefore, the UE in the ECM-IDLE state performs a UE based mobilityassociated procedure such as cell selection or cell reselection withoutthe need for receiving a command of the network. On the contrary, whenthe UE is in the ECM-CONNECTED state, the mobility of the UE is managedby the command of the network. When the position of the UE in theECM-IDLE state is different from a position which the network knows, theUE notifies a corresponding position of the UE to the network through atracking area update procedure.

Next, the system information will be described.

The system information includes required information which the UE needsto know to access the base station. Therefore, the UE needs to receiveall of the system information before accessing the base station andfurther, the UE continuously needs to have latest system information. Inaddition, since the system information is information which all UEs inone cell need to know, the base station periodically transmits thesystem information.

According to Phrase 5.2.2 of 3GPP TS 36.331 V8.7.0 (2009-09) “RadioResource Control (RRC); Protocol specification (Release 8)”, the systeminformation is divided in to a master information block (MIB), ascheduling block (SB), and a system information block (SIB). The MIBallows the UE to know a physical component, for example, a bandwidth.The SB allows the UE to know transmission information of the SIBs, forexample, a transmission period, and the like. The SIB is an aggregate ofassociated system information. For example, any SIB includes onlyinformation on a neighboring cell and any SIB includes only informationon a uplink wireless channel used by the UE.

In general, a service which the network provides to the UE may bedivided into three types. Further, the UE differently recognizes even atype of the cell by considering which service the UE receives. Theservice type will be first described below and thereafter, the type ofthe cell will be described.

Limited service: The service may provide an emergency call and anearthquake and Tsunami warning system (ETWS), and provide the emergencycall and the earthquake and Tsunami warning system (ETWS) in anacceptable cell.

Normal service: The service may mean a public use general service andmay provide the public use general service in a suitable or normal cell.

Operator service: The service may mean a service for a communicationnetwork operator and only the communication network operator may use thecell and a general user may not use the cell.

The type of the cell may be divided as below in association with theservice type provided by the cell.

1) Acceptable cell: Cell where the UE may receive the limited service.The cell is a cell that is not barred in terms of the corresponding UEand satisfies a cell selection criterion of the UE.

2) Suitable cell: Cell where the UE may receive the suitable service.The cell satisfies a condition of the acceptable cell andsimultaneously, satisfies additional conditions. As the additionalconditions, the cell needs to belong to a public land mobile network(PLMN) which the corresponding UE may access and needs to be a cellwhere execution of the tracking area update procedure of the UE is notbarred. When the corresponding cell is the CSG cell, the correspondingcell needs to be a cell where the UE may access the cell as a CSGmember.

3) Barred cell: The cell is a cell where information indicating that thecorresponding cell is a cell barred through the system information isbroadcasted.

4) Reserved cell: The cell is a cell where information indicating thatthe corresponding cell is a cell reserved through the system informationis broadcasted.

FIG. 4 is a flowchart illustrating an operation of a UE in an RRC idlestate. FIG. 4 illustrates a procedure of registering a UE of whichinitial power is turned on in the network through a cell selectionprocess and thereafter, cell reselection is performed as necessary.

Referring to FIG. 4, the UE selects radio access technology (RAT) forcommunicating with the public land mobile network from which the UEitself intends to receive the service (S410). Information on the PLMNand the RAT may be selected by a user of the UE and the informationstored in a universal subscriber identity module (USIM) may be used.

The UE selects a cell having a largest value among cell having measuredlarger signal intensity or quality than specific values (cell selection)(S420). The UE of which power is turned on performs the cell selectionand the execution of the cell selection may be called initial cellselection. A cell selection procedure will be described below in detail.After the cell selection, the UE receives the system information whichthe base station periodically sends. The aforementioned specific valuerepresents a value defined in the system in order to receive anassurance for quality of a physical signal in transmitting/receivingdata. Therefore, the value may vary depending on the applied RAT.

When network registration is required, the UE performs a networkregistration procedure (S430). The UE registers its own information(e.g., IMSI) in order to receive a service (e.g., paging)n from thenetwork. The UE does not register the information in the accessednetwork whenever selecting the cell, and registers the information wheninformation (e.g., a tracking area identity (TAI) of the network thatreceives from the system information) is different from information on anetwork known by the UE).

The UE performs the cell reselection based on a service environmentprovided by the cell or an environment of the UE (S440). When a value ofmeasured intensity or quality of the signal from a base station fromwhich the UE receives the service is smaller than a value measured froma base station of a neighboring cell, the UE selects one of other cellsthat provide a more excellent signal feature than the cell of the basestation accessed by the UE. This process is distinguished from theinitial cell selection as Process No. 2 to be cell re-selection. In thiscase, a temporal constraint is given in order to prevent the cell frombeing frequently reselected with the variation of the signal feature. Acell selection procedure will be described below in detail.

FIG. 5 is a flowchart illustrating a process of establishing an RRCconnection.

The UE sends to the network an RRC connection request message forrequesting the RRC connection (S510). The network sends an RRCconnection setup message as a response to the RRC connection request(S520). The UE enters an RRC connection mode after receiving the RRCconnection setup message.

The UE sends to the network an RRC connection setup complete messageused to verify successful completion of establishing the RRC connection(S530).

FIG. 6 is a flowchart illustrating a process of reconfiguring the RRCconnection. The RRC connection reconfiguration is used to modify the RRCconnection. The RRC connection reconfiguration is used for perform RBestablishment/modification/release, handover, and measurementsetup/modification/release.

The network sends to the UE an RRC connection setup message formodifying the RRC connection (S610). The UE sends to the network an RRCconnection reconfiguration complete message used to verify successfulcompletion of establishing the RRC connection reconfiguration as aresponse to the RRC connection reconfiguration (S620).

Hereinafter, a radio link failure will be described.

The UE performs continuously performs measurement for the quality of aradio link with the serving cell that receives the service. The UEdecides whether communication is impossible under a current situationdue to deterioration in quality of the radio link with the serving cell.When the communication is almost impossible due to too low quality ofthe serving cell, the UE decides the current situation as a wirelessconnection failure.

When a radio link failure is decided, the UE abandons maintainingcommunication with a current serving cell, selects a new cell throughthe cell selection (alternatively, cell reselection) procedure, andattempts RRC connection re-establishment to a new cell.

FIG. 7 is an exemplary diagram illustrating a radio link failure. Anoperation associated with the radio link failure may be described as twophases.

In a first phase, the UE is in a normal operation and checks whetherthere is a problem in a current communication link. When the problem isdetected, the UE declares a radio link problem and waits for recovery ofthe radio link for a first stand-by time T1. When the radio link isrecovered until the first stand-by time elapses, the UE performs thenormal operation again. When the radio link is not recovered until thefirst stand-by time is expired, the UE declares the radio link failureand the UE enters a second phase.

In the second phase, the UE waits for recovering the radio link for thesecond stand-by time T2. When the radio is not recovered until thesecond stand-by time is expired, the UE enters the RRC idle state.Alternatively, the UE may perform the RRC re-establishment procedure.

The RRC connection re-establishment procedure is a procedure ofre-establishing the RRC connection again in the RRC_CONNECTED state.Since the UE stays in the RRC_CONNECTED state, that is, since the UEdoes not enter the RRC_IDLE state, the UE does not initialize all ofradio configurations (e.g., radio bearer configurations) thereof.Instead, when the UE starts the RRC connection reconfigurationprocedure, the UE temporarily suspends using all of the radio bearersexcept for SRB0. When the RRC connection reconfiguration is succeeded,the UE resumes using the radio bearers of which the use is temporarilysuspended.

FIG. 8 is a flowchart illustrating a success in a process ofreestablishing a connection.

The UE selects a cell by performing the cell selection. The UE receivesthe system information in order to receive basic parameters foraccessing the cell in the selected cell. In addition, the UE sends tothe base station the RRC connection reestablishment request message(S810).

When the selected cell is a cell having a context of the UE, that is, aprepared cell, the base station permits the RRC connectionreestablishment request of the UE and sends to the UE the RRC connectionreestablishment message (S820). The UE sends to the base station the RRCconnection reestablishment complete message to succeed in the RRCconnection re-establishment procedure (S830).

FIG. 9 is a flowchart illustrating a failure in the process ofreestablishing the connection. The UE sends to the base station the RRCconnection reestablishment request message (S810). When the selectedcell is not the prepared cell, the base station sends an RRC connectionre-establishment reject message to the UE as a response to the RRCconnection reestablishment request (S815).

Next, a procedure in which the UE selects the cell will be described indetail.

When the power of the UE is turned on or the UE stays in the cell, theUE performs procedures for receiving the service byselecting/reselecting a cell having appropriate quality.

The UE in the RRC idle state needs to prepare for receiving the servicethrough the cell by continuously selecting the cell having theappropriate quality. For example, the UE of which the power is justturned on needs to select the cell having the appropriate quality forregistration in the network. When the UE in the RRC connection stateenters the RRC idle state, the UE needs to select a cell to stay in theRRC idle state. As such, a process in which the UE selects a cell thatsatisfies a predetermined condition in order to stay in a servicestand-by state such as the RRC idle state is referred to as the cellselection. Since the UE performs the cell selection while the cell inthe RRC idle state may not be decided at present, it is important toselect the cell rapidly as possible. Therefore, in the case of a cellthat provides radio signal quality having a predetermined reference ormore, even though the cell is not a cell that provides the best radiosignal quality for the UE, the cell may be selected in the cellselection process by the UE.

Hereinafter, a method and a procedure for selecting the cell by the UEin the 3GPP LTE will be described in detail with reference to 3GPP TS36.304 V8.5.0 (2009-03) “User Equipment (UE) procedures in idle mode(Release 8)”.

When the power of the UE is turned on at an initial stage, the UEretrieves the public land mobile network (PLMN) and selects anappropriate PLMN capable of receiving the service. The PLMN is a networkthat is deployed or operated by a mobile network operator. Each mobilenetwork operator operates one or more PLMNs. The respective PLMNs may beidentified by a mobile country code (MCC) and a mobile network code(MNC). PLMN information of the cell is included in the systeminformation and broadcasted. The UE attempts to register the selectedPLMN. When the registration is succeeded, the selected PLMN becomes aregistered PLMN (RPLMN). The network may signal a PLMN list to the UEand the PLMNs included in the PLMN list may be considered as the PLMNsuch as the RPLMN. The UE registered in the network needs to bereachable by the network. When the UE is in the ECM-CONNECTED state(similarly, the RRC connection state), the network recognizes that theUE receives the service). However, when the UE is in the ECM-IDLE state(similarly, the RRC idle state), a situation of the UE is not effectivein the eNB, but the situation is stored in the MME. In this case, theposition of the UE which is in the ECM-IDLE state is known to only theMME as granularity of a list of tracking areas (TAs). A single TA isidentified by a tracking area identity configured by the PLMN identityto which the TA belongs and the tracking area code (TAC) uniquelyexpressing the TA in the PLMN.

Subsequently, the UE selects a cell having signal quality and feature toreceive an appropriate service among cells provided by the selectedPLMN.

The cell selection process is generally divided into two types.

First, as an initial cell selection process, the UE has no advanceinformation on the radio channel during this process. Therefore, the UEretrieves all radio channels in order to find the appropriate cell. TheUE finds the strongest cell in each channel. Thereafter, the UE selectsthe corresponding cell only at the time of finding the suitable cellthat satisfies the cell selection criterion.

Next, the UE may select the cell by using stored information or usinginformation broadcasted in the cell. Therefore, the cell selection maybe rapidly performed as compared with the initial cell selectionprocess. When the UE only finds the cell that satisfies the cellselection criterion, the UE selects the corresponding cell. When the UEdoes not find the suitable cell that satisfies the cell selectioncriterion through such a process, the UE performs the initial cellselection process.

After the UE selects a predetermined cell through the cell selectionprocess, the strength or quality of the signal between the UE and thebase station may be changed due to the mobility of the UE or a change ofa wireless environment. Therefore, when the quality of the selected celldeteriorates, the UE may select another that provides higher quality.When the cell is again selected as such, a cell that provides highersignal quality than the currently selected cell is generally selected.The process is referred to as the cell reselection. The cell reselectionprocess generally has a basic object o select the cell having thehighest quality to the UE.

In addition to the quality of the radio signal, the network decides apriority for each frequency to notify the priority to the UE. The UEthat receives the priority preferentially considers the priority to aradio signal quality criterion during the cell reselection process.

There may be a method for selecting or reselecting the cell according tothe signal feature of the wireless environment and there may be a cellreselection method described below according to the features of the RATand the frequency of the cell.

-   -   Intra-frequency cell reselection: The UE reselect a cell having        the same RAT and the same center-frequency as a cell which is        being camping.    -   Inter-frequency cell reselection: The UE reselects a cell having        the same RAT and a different center-frequency as the cell which        is being camping.    -   Inter-RAT cell reselection: The UE reselect a cell using an RAT        different from an RAT which is being camping.

A principle of the cell reselection process will be described below.

First, the UE measures the qualities of the serving cell and theneighboring cell for the cell reselection.

Second, the reselection is performed based on the cell reselectioncriterion. The cell reselection criterion has features described belowin association with the measurement of the serving cell and theneighboring cell.

The intra-frequency cell reselection is basically based on ranking. Theranking defines an index value for evaluating the cell reselection andthe cells are ordered in the order of the index value by using the indexvalue. A cell having the best index is generally called a best rankedcell. The cell index value is based on a value which the UE measures forthe corresponding cell and is applied with a frequency offset or a celloffset as necessary.

The inter-frequency cell reselection is based on a frequency priorityprovided by the network. The UE attempts to camp on a frequency havingthe highest frequency priority. The network may provide the frequencypriority to which in-cell UEs will commonly apply through broadcastsignaling or provide a frequency-dedicated priority for each UE throughUE-dedicated signaling.

The network may provide a parameter (e.g., a frequency-specific offset)used for the cell reselection to the UE for the inter-frequency cellreselection for each frequency.

The network may provide a neighboring cell list (NCL) used for the cellreselection to the UE for the intra-frequency cell reselection or theinter-frequency cell reselection. The NCL includes a cell-specificparameter (e.g., cell-specific offset) used in the cell reselection.

The network may provide a cell reselection black list used for the cellreselection to the UE for the intra-frequency cell reselection or theinter-frequency cell reselection. The UE does not perform the cellreselection for a cell included in the black list.

Subsequently, the ranking performed during the cell reselectionevaluating process will be described.

A ranking criterion used to give the priority of the cell is defined asillustrated in Equation 1.

R _(S) =Q _(meas,s) +Q _(hyst) ,R _(n) =Q _(meas,n) −Q_(offset)  [Equation 1]

Herein, Rs represents a ranking criterion of the serving cell, Rnrepresents a ranking criterion of the neighboring cell, Qmeas,srepresents a quality value which the UE measures for the serving cell,Qmeas,n represents a quality value which the UE measures for aneighboring cell, Qhyst represents a hysteresis value for the ranking,and Qoffset represents an offset between two cells.

In an intra-frequency, when the UE receives an offset Qoffsets,n betweenthe serving cell and the neighboring cell, Qffoset=Qoffsets,n and whenthe UE does not receive Qoffsets,n, Qoffset=0.

In an inter-frequency, when the UE receives the offset Qoffsets,n firthe corresponding cell, Qoffset=Qoffsets,n+Qfrequency and when the UEdoes not receive Qoffsets,n, Qoffset=Qfrequency.

When the ranking varies while the ranking criterion Rs of the servingcell and the ranking criterion of the neighboring cell Rn are similar toeach other, the ranking is frequently reversed, and as a result, the UEmay alternatively reselect both cells. Qhyst represents a parameter forpreventing the UE from alternatively reselecting both cells by givinghysteresis in cell reselection.

The UE measures the Rs of the serving cell and the Rn of the neighboringcell according to the above equation and regards a cell having thelargest ranking criterion value as the best ranked cell and reselectsthis cell.

According to the criterion, it can be seen that the quality of the cellacts as the most important criterion in the cell reselection. If thereselected cell is not the suitable cell, the UE excludes thecorresponding frequency or the corresponding cell from a cellreselection target.

Hereinafter, a measurement and a measurement report will be described.

Supporting the mobility of the UE is required in the mobilecommunication system. Therefore, the UE continuously measures a qualityfor a serving cell that provides the service at present and a qualityfor a neighboring cell. The UE reports a measurement result to thenetwork at an appropriate time and the network provides optimal mobilityto the UE through handover. A measurement for the object is often calleda radio resource management (RPM) measurement.

The UE may perform a measurement having a specific object set by thenetwork and report a result of the measurement to the network in orderto provide information that may help an operator to operate the networkin addition to the object of supporting the mobility. For example, theUE receives broadcast information of a specific cell decided by thenetwork. The UE may report a cell identity (also referred to as a globalcell identity) of the specific cell, identification information (forexample, tracking area code) to which the specific cell belongs, and/orother cell information (for example, whether the specific cell is amember of the closed subscriber group (CSG) cell) to the serving cell.

When the UE which is moving verifies that a quality of a specific regionis too bad through the measurement, positional information on cellshaving a bad quality and a measurement result may be reported to thenetwork. The network may attempt optimization of the network based onreporting of measurement results of UEs that help operating the network.

In the mobile communication system in which a frequency reuse factor is1, mobility is generally made among different cells in the samefrequency band. Therefore, in order to well assure the mobility of theUE, the UE may well measure the qualities and cell information of theneighboring cells having the same center-frequency as the serving cell.A measurement for a cell having the same center-frequency as the servingcell as such is called an intra-frequency measurement. The UE reports ameasurement result to the network at an appropriate time by performingthe intra-frequency measurement to achieve an object of thecorresponding measurement result.

The mobile communication operator may operate the network by using aplurality of frequency bands. When the service of the communicationsystem is provided through the plurality of frequency bands, the UEneeds to be able to measure the qualities and cell information of theneighboring cells having a different center-frequency from the servingcell for assuring the optimized mobility for the UE. A measurement for acell having the different center-frequency as the serving cell as suchis called an inter-frequency measurement. The UE needs to be able toreport a measurement result to the network at an appropriate time byperforming the inter-frequency measurement.

When the UE supports a measurement for heterogeneous networks, the UEmay perform a measurement for cells of the heterogeneous networks by abase station configuration. The measurement for the heterogeneousnetworks is called an inter-radio access technology (RAT) measurement.For example, the RAT may include a UMTS terrestrial radio access network(UTRAN) and a GSM edge radio access network (GERAN) that follows a 3GPPstandard specification, and may include even a CDMA 2000 system thatfollows a 3GPP2 standard specification.

FIG. 10 is a flowchart illustrating the existing measurement performingmethod.

The UE receives measurement configuration information from the basestation (S1010). A message including the measurement configurationinformation is referred to as a measurement configuration message. TheUE performs a measurement based on the measurement configurationinformation (S1020). When a measurement result satisfies a reportingcondition in the measurement configuration information, the UE reportsthe measurement result to the base station (S1030). A message includingthe measurement result is referred to as a measurement report message.

The measurement configuration information may include informationdescribed below.

(1) Measurement object information: Represents information on an objectfor which the UE will perform the measurement. A measurement objectincludes at least one among an intra-frequency measurement object whichis an object of an intra-measurement, an inter-frequency measurementobject which is an object of an inter-measurement, and an inter-RATmeasurement object which is an object of an inter-RAT measurement. Forexample, the intra-frequency measurement object may indicate aneighboring cell having the same frequency band as the serving cell, theinter-frequency measurement object may indicate a neighboring cellhaving a different frequency band from the serving cell, and theinter-RAT measurement object may indicate a neighboring cell havingdifferent RAT from the serving cell.

(2) Reporting configuration information: Represents information on areporting condition and a report type regarding when the UE reports themeasurement result. The reporting condition may include information onan event or a cycle that triggers reporting the measurement result. Thereport type represents information regarding in which type themeasurement result is configured.

(3) Measurement identity information: Represents information on ameasurement identity to decide which measurement object, at a time when,and in which type the UE reports by associating the measurement objectwith the report configuration. The measurement identity information isincluded in the measurement report message, and as a result, it can beseen that for which measurement object the measurement result is andunder which reporting condition the measurement report occurs.

(4) Quantity configuration information: Represents information on aparameter for configuring filtering a measurement unit, a report unit,and/or a measurement result value.

(5) Measurement gap information: Represents information on a measurementgap which is an interval which the UE may use for only a measurementwithout considering data transmission with the serving cell becausedownlink transmission or uplink transmission is not scheduled.

The UE has a measurement object list, a measurement report configurationlist, and a measurement identity list in order to perform a measurementprocedure.

In the 3GPP LTE, the base station may configure only one measurementobject for one frequency band to the UE. According to Phrase 5.5.4 of3GPP TS 36.331 V8.5.0 (2009-03) “Evolved Universal Terrestrial RadioAccess (E-UTRA) Radio Resource Control (RRC); Protocol specification(Release 8)”, events that trigger a measurement report illustrated in atable described below are defined.

TABLE 1 Events Reporting conditions Event A1 Serving becomes better thanthreshold Event A2 Serving becomes worse than threshold Event A3Neighbour becomes offset better than serving Event A4 Neighbour becomesbetter than threshold Event A5 Serving becomes worse than threshold1 andneighbour becomes better than threshold2 Event B1 Inter RAT neighbourbecomes better than threshold Event B2 Serving becomes worse thanthreshold1 and inter RAT neighbour becomes better than threshold2

When the measurement result by the UE satisfies the configured event,the UE transmits the measurement report message to the base station.

FIG. 11 illustrates one example of a measurement configurationconfigured for the UE.

First, a measurement identity 1 1101 connects an intra-frequencymeasurement object and a report configuration 1 to each other. The UEperforms an intra frequency measurement and the report configuration 1is used to decide a criterion and a type of reporting a measurementresult.

A measurement identity 2 1102 is connected with the intra-frequencymeasurement object similarly as the measurement identity 1 1101, butconnects the intra-frequency measurement object to a reportconfiguration 2. The UE performs the intra frequency measurement and thereport configuration 2 is used to decide the criterion and the type ofreporting the measurement result.

The UE transmits the measurement result even though the measurementresult for the intra-frequency measurement object satisfies any one ofthe report configuration 1 and the report configuration 2, by themeasurement identity 1 1101 and the measurement identity 2 1102.

A measurement identity 3 1103 connects an inter-frequency measurementobject 1 and a report configuration 3 to each other. When a measurementresult for the inter-frequency measurement object 1 satisfies thereporting condition included in the report configuration 3, the UEreports the measurement result.

A measurement identity 4 1104 connects an inter-frequency measurementobject 2 and the report configuration 2 to each other. When ameasurement result for the inter-frequency measurement object 2satisfies the reporting condition included in the report configuration2, the UE reports the measurement result.

Meanwhile, the measurement object, the report configuration, and/or themeasurement identity may be added, changed, and/or deleted. Theaddition, the change, and/or the deletion may be instructed by sending anew measurement configuration message or sending a measurementconfiguration change message to the UE.

FIG. 12 illustrates an example of deleting a measurement identity. Whenthe measurement identity 2 1202 is deleted, a measurement for ameasurement object associated with the measurement identity 2 1202 isstopped and a measurement report is not also transmitted. Themeasurement object or the report configuration associated with thedeleted measurement identity may not be changed.

FIG. 13 illustrates an example of deleting a measurement object. Whenthe inter-frequency measurement object 1 is deleted, the UE also deletesthe associated measurement identity 3 1303. The measurement for theinter-frequency measurement object 1 is stopped and the measurementreport is not also transmitted. However, the report configurationassociated with the deleted first inter-frequency measurement object maynot be changed or deleted.

When the report configuration is removed, the UE removes even theassociated measurement identity. The UE stops measuring the associatedmeasurement object by the associated measurement identity. However, themeasurement object associated with the deleted report configuration maynot be changed or deleted.

The measurement report may include the measurement identity, a measuredquality of the serving cell, and a measurement result of the neighboringcell. The measurement identity identifies a measurement object in whichthe measurement report is triggered. The measurement result of theneighboring cell may include a cell identity and a measured quality ofthe neighboring cell. The measured quality may include at least one ofreference signal received power (RSRP) and reference signal receivedquality (RSRQ).

Subsequently, H(e)NB will be described.

The mobile communication service may be provided through a person, aspecific operator, or a base station possessed by a group in addition tothe mobile communication network operator. The base station is calledHome NB (HNB) or Home eNB (HeNB). Hereinafter, both the HNB and HeNB arecollectively the HeNB. The HeNB aims at basically providing a servicespecialized to only a closed subscriber group (CSG). However, theservice may be provided to users other than the CSG according to aconfiguration of an operating mode of the HeNB.

FIG. 14 is a diagram illustrating one example of a wirelesscommunication system illustrating an HeNB operation.

Referring to FIG. 14, a Home eNB gateway (HeNB GW) may be operated inorder to service the HeNB as such. The HeNBs is connected to the EPCthrough the HeNB GW or connected directly to the EPC. The HeNB GW isseen as a general eNB for the MME. The HeNB GW is seen as the MME forthe HeNB. Therefore, the HeNB and the HeNB GW are connected to eachother through an S1 interface and the HeNB GW and the EPC are alsoconnected to each other through the S1 interface. Further, even when theHeNB and the EPC are directly connected to each other, the HeNB and theEPC are connected to each other through the S1 interface. Most functionsof the HeNB are similar to those of a general eNB.

In general, the HeNB is lower than an eNB possessed by the mobilecommunication operator in radio transmission output. Therefore, servicecoverage provided by the HeNB is generally smaller than that provided bythe eNB. Due to such a feature, a cell provided by the HeNB is oftenclassified as a femto cell as compared with a macro cell provided by theeNB in terms of the service coverage. Meanwhile, in terms of theprovided service, when the HeNB provides the service to only the CSG,the cell provided by the HeNB is called a CSG cell.

Each CSG has its own unique identification number and the identificationnumber is called a CSG identity (ID). The UE may have a list of the CSGto which the UE belongs as a member and the CSG list may be changed by arequest from the UE or a command of the network. In general, one HeNBmay support one CSG.

The HeNB transfers a CSG ID of a CSG supported thereby through thesystem information to be accessed by only the member UE of thecorresponding CSG. When the UE discovers the CSG cell, the UE may verifywhich CSG the CSG cell supports by reading the CSG ID included in thesystem information. The UE that reads the CSG ID regards thecorresponding cell as a cell capable of access only when the UE itselfis a member of the corresponding CSG cell.

Even the HeNB need not permit only the CSG UE to access itself. The HeNBmay also permit a UE which is not the CSG member to access itselfaccording to a configuration of the HeNB. Which UE the HeNB permits toaccess itself depends on the configuration of the HeNB and herein, theconfiguration means a configuration of an operating mode of the HeNB.The operating mode of the HeNB is divided into three types describedbelow by considering which UE the HeNB provides the service to.

Closed access mode: Represents a mode to provide the service to aspecific CSG member. The HeNB provides the CSG cell.

Open access mode: Represents a mode to provide the service without alimitation of the specific CSG member like a general eNB. The HeNBprovides not the CSG cell but the general cell.

Hybrid access mode: Represents a mode to provide a CSG service to thespecific CSG member and provide the service to even a non-CSG memberlike the general cell. Recognized as the CSG cell by the CSG member UEand recognized as the general cell by the non-CSG member UE. Such a cellis called a hybrid cell.

The HeNB notifies whether a cell serviced thereby is the CSG cell or thegeneral cell to the UE to allow the UE to know whether the UE may accessthe corresponding cell. The HeNB operated in the closed access modebroadcasts that the HeNB itself is the CSG cell through the systeminformation. The HeNB operated in the open access mode broadcasts thatthe HeNB itself is not the CSG cell through the system information. Assuch, the HeNB encapsulates a 1-bit CSG indicator indicating whether thecell serviced thereby is the CSG cell in the system information. Forexample, the HeNB broadcasts that the serviced cell is the CSG cell bysetting the CSG indicator as TRUE. If the serviced cell is not the CSGcell, the CSG indicator may be set as FALSE or a method that skipstransmitting the CSG indicator may be used. Since the UE needs to beable to distinguish the general cell provided by the eNB from the CSGcell, the general eNB also transmit the CSG indicator to allow the UE toknow that the cell type provided thereby is the general cell. Thegeneral eNB does not transmit the CSG indicator to allow the UE to knowthat the cell type provided thereby is the general cell. Table 2illustrates a CSG associated parameter transmitted in a correspondingcell for each cell type. Subsequently, Table 3 illustrates a type of aUE that permits the access for each cell type.

TABLE 2 CSG cell General cell CSG indicator Indicating ‘CSG cell’Indicating ‘Non-CSG cell’ or not transmitted CSG identity Transmittingsupported Not transmitted CSG identity

TABLE 3 CSG cell General cell UE not supporting CSG InaccessibleAccessible Non-CSG member UE Inaccessible Accessible Member CSG UEAccessible Accessible

Hereinafter, inter-cell interference coordination (ICIC) will bedescribed.

The ICIC is a task that operates a radio resource so that a control ofinter-cell interference is maintained. An ICIC mechanism may be dividedinto frequency-domain ICIC and time-domain ICIC. The ICIC has amulti-cell radio resource management (RRM) function to requireconsidering information from multiple cells.

An interfering cell is a cell that provides interference. Theinterfering cell is also referred as an aggressor cell.

An interfered cell is a cell that is interfered by the interfering cell.The interfered cell is also referred to as a victim cell.

The frequency-domain ICIC coordinates the use of a frequency-domainresource (e.g., a resource block (RB)) among the multiple cells.

The time-domain ICIC coordinates a time-domain resource (e.g., asubframe) among the multiple cells. An operations, administration, andmaintenance (OAM) configuration called an almost blank subframe (ABS)pattern may be used for the time-domain ICIC. An ABS in the interferingcell is used to protect a resource in the subframe in the interferedcell that receives interference among strong cells. The ABS is asubframe that has reduced transmission power (alternatively, zerotransmission power) on the physical channel or has reduced activity.

A pattern based on the ABS is notified to the UE and restricts a UEmeasurement. This restriction is referred to as a measurement resourcerestriction. The ABS pattern represents information indicating whichsubframe is the ABS in one or more radio frames.

There are provided three measurement resource restriction patternsaccording to a measured cell (e.g., a serving cell or a neighbor cell)and measurement types (e.g., a radio resource management (RRM), a radiolink measurement (RLM), and channel state information (CSI)).

‘ABS pattern 1’ is used in an RRM/RLM measurement resource restrictionof the serving cell. The base station may notify information on ABSpattern 1 to the UE in configuration/modification/release of the RB orwhen MAC/PHY configuration is modified.

‘ABS pattern 2’ is used in an RRM measurement resource restriction ofthe neighbor cell that operates at the same frequency as the servingcell. Therefore, a list of neighbor cells to be measured in addition toinformation on ABS pattern 2 may be provided to the UE. ABS pattern 2may be included in a measurement configuration for a measurement object.

‘ABS pattern 3’ is used in a resource restriction for a CSI measurementof the serving cell. ABS pattern 3 may be included in a message forconfiguring a CSI report.

Two scenarios of a CSG scenario and a pico scenario are considered forthe ICIC.

FIG. 15 exemplifies a CSG scenario.

The CSG cell represents a cell accessible by only a specific subscriber.The non-member UE as a UE which is not the member of the CSG cell is UEthat does not access the CSG cell. The CSG cell which the UE may notaccess is referred to as the non-member CSG cell. The macro cellrepresents the serving cell of the non-member UE. Coverage of the CSGcell and coverage of the macro cell are partially or fully duplicatedwith each other.

A primary interference condition occurs when the non-member UE ispositioned in close proximity with the CSG cell. In terms of thenon-member UE, the interfering cell becomes the CSG cell and the macrocell becomes the interfered cell. The time-domain ICIC is used so as forthe non-member UE to continuously receive the service in the macro cell.

In the RRC connection state, when the network discovers that thenon-member UE belongs to strong interference from the CSG cell, thenetwork may configure a measurement resource restriction. Further, inorder to facilitate mobility from the macro cell, the network mayconfigure an RRM measurement resource restriction for the neighbor cell.When the UE is not strongly interfered from the CSG cell any longer, thenetwork may release the RRM/RLM/CSI measurement resource restriction.

The UE may use the measurement resource restrictions configured for theRRM, RLM, and CSI measurement. That is, a resource for the RLM may beused in the ABS, and the measurement for the RLM and the CSI measurementmay be performed in the ABS.

The network may configure the CSG cell not to use a low-interferenceradio resource depending on the configured measurement resourcerestriction. That is, the CSG cell may not transmit or receive data inthe ABS.

FIG. 16 exemplifies a pico scenario.

A pico cell is a serving cell of a pico UE. The pico cell is a cell ofwhich coverage is partially or fully duplicated with the coverage of themacro cell. The pico cell may generally have smaller coverage than themacro cell, but the present invention is not particularly limitedthereto.

The primary interference condition occurs when the pico UE is positionedat an edge of the pico serving cell. In terms of the pico UE, theinterfering cell becomes the macro cell and the pico cell becomes theinterfered cell. The time-domain ICIC is used so as for the pico UE tocontinuously receive the service in the pico cell.

When the pico cell discovers that the pico UE is strongly interferedfrom the macro cell, the pico cell may configure the measurementresource restriction for the corresponding UE.

The pico UE may use the measurement resource restrictions configured forthe RRM, RLM, and CSI measurement. That is, the resource for the RLM maybe used in the ABS, and the measurement for the RLM and the CSImeasurement may be performed in the ABS. When the pico cell is stronglyinterfered from the macro cell, a more accurate measurement is possiblein the case where the RRM/RLM/CSI measurement is performed in the ABS.

Further, when the UE in the macro cell as the serving cell performs themeasurement for the neighbor cell in the ABS, mobility from the macrocell to the pico cell may be facilitated.

The UE performs the RRM measurement such as the reference signalreceived power (RSRP) and the reference signal received quality (RSRQ),a measurement of quality such as a channel quality indicator (CQI), anda path-loss measurement for the serving cell or the neighbor cell.Further, the UE may perform a measurement for radio link monitoring(RLM) for monitoring a connection with the serving cell.

The interfering cell and the interfered cell are decided depending on anobject which the UE intends to measure.

When the UE intends to measure the serving cell, an intra-frequencyneighbor cell having a high signal strength near the UE may act asinterference in a measurement for the serving cell. In this case, the UEmay undergo strong interference by the neighbor cell in the measurementfor the serving cell.

When the UE intends to measure the intra-frequency neighbor cell,serving cell and other intra-frequency neighbor cell signals may act asthe interference for the measurement of the intra-frequency neighborcell. In this case, the UE may undergo strong interference by theserving cell and other neighbor cells of a serving frequency in themeasurement of the neighbor cell.

When the serving cell may know information on a measurement resourcerestriction which the neighbor cell causing the UE to be interferedapplies for suppressing the interference, the interfered UE may performa limited measurement based on the measurement resource restriction. Theserving cell may provide the service the UE through scheduling primarilyusing a low-interference radio resource in spite of the interference bythe neighbor cell.

A multimedia broadcast/multicast service (MBMS) is a service to providemultimedia data to the UE in the cell. An MCH channel which is atransmission channel for the MBMS may be mapped to the MCCH or the MTCHwhich is the logical channel. The MCCH transmits an RRC messageassociated with the MBMS and the MTCH transmits traffic of a specificMBMS.

A plurality of MCHs may be used according to capacities of the MTCH andthe MCCH in one cell. The MCH is in charge of transmitting two logicalchannels of the MTCH and the MCCH, and is again mapped to a physicalmulticast channel (PMCH) which is the physical channel.

One MCCH is present in one MBMS single frequency network (MBSFN) regiontransmitting the same MBMS information/traffic, and when a plurality ofMBSFN regions are provided in one cell, the UE may receive a pluralityof MCCHs. When the MBMS associated RRC message is changed in a specificMCCH channel, the PDCCH transmits an MBMS radio network temporaryidentity (M_RNTI) and an indicator indicating the specific MCCH.

A UE that supports the MBMS receives the M-RNTI and the MCCH indicatorthrough the PDCCH to determine that the MBMS associated RRC message ischanged in the specific MCCH and receive the specific MCCH. The RRCmessage of the MCCH may be changed every change cycle and is repeatedlybroadcasted every repetition cycle.

The existing wireless network may calculate the number of UEs thatreceives a specific service through a counting procedure. The countingprocedure is configured in such a manner that the UE transmits an uplinkcounting response message when the wireless network transmits a downlinkcounting request message.

When a UE receives a request for reporting system information of aneighboring cell from a serving cell, the UE temporarily acquires thesystem information of the neighboring cell by accessing the neighboringcell by leaving the serving cell. Thereafter, the UE performs aprocedure of reporting neighboring cell information to the serving cellby accessing the serving cell again. While the UE leaves the servingcell in order to acquire the system information, the UE corresponds toan unreachable object from the viewpoint of the serving cell, and as aresult, the serving cell may not transfer even any command/message/datato the UE.

In the case of a specific handover, the serving cell requests systeminformation of a handover target cell to the UE. A long time may elapseuntil the UE receives the system information of the neighboring cell andreports the received system information to the serving cell. As aresult, a problem in which the handover is delayed may occur.

Meanwhile, the UE may have already had system information of acorresponding neighboring cell before receiving a request for reportingthe system information of the neighboring cell from the serving cell. Ifthe system information of the neighboring cell is valid even whenreporting the system information is requested, separately acquiring thesystem information by accessing the neighboring cell may be anunnecessary procedure. In this case, the UE may transmit the systeminformation of the neighboring cell which the UE has already had to theserving cell, and as a result, an effect to rapidly perform the handovermay be brought through rapid reporting of the system information.Hereinafter, the method for reporting system information will bedescribed in more detail.

FIG. 17 is a flowchart illustrating an operation of a UE that performsthe method for reporting system information according to an embodimentof the present invention.

Referring to FIG. 17, the UE receives a system information reportingrequest to request reporting the system information of the neighboringcell from the serving cell (S1710).

The UE determines whether there is system information of the neighboringcell which is acquired in advance. The procedure of determining whetherthere is the system information which is acquired in advance may includea step of determining whether the UE has the system information which isobtained in advance before receiving the request for reporting thesystem information and a step of determining whether the correspondingsystem information is valid when there is the system information of theneighboring cell which has already been obtained.

Whether the system information of the neighboring cell which is obtainedin advance is valid may be determined depending on a time elapsed fromthe time when the system information is obtained. When the elapsed timeis more than a specific value, it may be that the corresponding systeminformation is not valid any longer.

The UE reports the corresponding system information to the serving cellwhen there is the system information regarding the neighboring cellacquired in advance, to be reported to the serving cell (S1730).

The UE acquires the system information from the neighboring cell whenthere is no system information of the neighboring cell to be reported tothe serving cell (S1740). The UE accesses the neighboring cell bytemporally leaving the serving cell in order to acquire the systeminformation of the neighboring cell. The UE may acquire the systeminformation of the neighboring cell through a broadcast channel byaccessing the neighboring cell.

The UE reports the system information acquired by accessing the servingcell to the serving cell again (S1750).

The UE receives a request for reporting the system information of theneighboring cell from the serving cell, and when the UE reports thesystem information which is acquired in advance before the request, theUE may transmit control information regarding the corresponding systeminformation to the serving cell together with the system informationreporting message. The control information may include an indicatorindicating that the corresponding system information is the systeminformation which is acquired in advance before the reporting requestand an indicator associated with an acquisition time.

FIG. 18 is a flowchart illustrating one example of a method forreporting system information according to an embodiment of the presentinvention. Referring to FIG. 18, it is assumed that the UE has alreadyhad system information of neighboring cell A and does not have systeminformation of neighboring cell B.

Referring to FIG. 18, the UE receives a system information reportingrequest to request reporting the system information of neighboring cellA from the serving cell (S1810).

Since the UE has the system information of neighboring cell A, the UEreports the system information of neighboring cell A to the serving cell(S1820). The UE may transmit to the serving cell both the systeminformation of neighboring cell A and the control information regardingthe system information. The control information may include an indicatorindicating that the corresponding system information is the systeminformation acquired in advance before receiving the system informationreporting request. The control information may include an indicatorindicating the time when the system information was acquired.

The UE receives a system information reporting request to requestreporting the system information of neighboring cell B from the servingcell (S1830).

Since the UE does not have the system information of neighboring cell B,the UE acquires the system information by accessing neighboring cell B(S1840).

The UE acquires the system information of neighboring cell B andthereafter, reports the acquired system information to the serving cell(S1850). Since the system information of cell B is newly acquired afterreceiving the system information reporting request, the controlinformation regarding the corresponding system information may not betransmitted together. On the contrary, the system information of cell Bmay be transmitted together with the control information, and in thiscase, the control information may include an indicator that the systeminformation of cell B is the system information obtained after receivingthe system information reporting request and/or an indicator indicatingthe time when the corresponding system information is acquired.

The UE may store system information of a specific neighboring cell for aspecific time or more in order to perform the system informationreporting method according to the embodiment of the present invention.When the UE receives system information of a cell which a specific userfrequently visits, for example, a cell installed in a home of the useror a cell installed in a company, the UE may store the systeminformation of the cell in order to report the system information of thecell afterwards. In the present invention, when the UE stores the systeminformation for the purpose of reporting the system information, the UEmay be allowed to store the system information for a time which is morethan a valid time of general system information.

Meanwhile, the serving cell may indicate to the UE whether systeminformation is allowed to be transmitted when the corresponding systeminformation obtained in advance regarding a specific neighboring cellexists. To this end, the serving cell may transmit to the UE aready-acquired system information report indicator together with thesystem information reporting request. When the ready-acquired systeminformation report indicator is used, the UE may report the systeminformation to the serving cell based thereon. A method for reportingsystem information based on the ready-acquired system information reportindicator will hereinafter be described in detail.

FIG. 19 illustrates an operating flowchart of a UE that performs themethod for reporting system information according to an embodiment ofthe present invention.

Referring to FIG. 19, the UE receives a system information reportingrequest to request reporting system information of a neighboring cellfrom the serving cell (S1910).

The UE determines whether to report system information which is acquiredin advance, based on the ready-acquired system information reportindicator included in the system information reporting request (S1920).When the ready-acquired system information report indicator is notincluded in the system information reporting request, the UE maydetermine that reporting the system information which is acquired inadvance is not allowed. Further, when the ready-acquired systeminformation report indicator is included in the system informationreporting request, the UE may determine that reporting the informationwhich is acquired in advance is allowed. Alternatively, when theready-acquired system information report indicator is included in thesystem information reporting request and the indicator is set toindicate that the system information which is acquired in advance isallowed, the UE may determine that reporting the system informationwhich is acquired in advance is allowed.

When reporting the system information which is acquired in advance isnot allowed, the UE acquires the system information from the neighboringcell (S1930). The UE accesses the neighboring cell by temporally leavingthe serving cell in order to acquire the system information of theneighboring cell. The UE may acquire the system information of theneighboring cell through a broadcast channel by accessing theneighboring cell.

The UE reports the system information acquired by accessing theneighboring cell to the serving cell (S1940).

When reporting the system information which is acquired in advance isallowed, the UE determine whether there is system information which isacquired in advance, to be reported to the serving cell (S1950).Determining whether there is the system information which is acquired inadvance may include a step of determining whether the UE has the systeminformation which is acquired in advance before receiving the requestfor reporting the system information and a step of determining whetherthe corresponding system information is valid when there is the systeminformation of the neighboring cell which has already been acquired.

Whether the system information of the neighboring cell which is acquiredin advance is valid may be determined depending on a time elapsed fromthe time when the system information is acquired. When the elapsed timeis more than a specific value, it may be that the corresponding systeminformation is not valid any longer.

The UE reports the corresponding system information to the serving cellwhen there is the system information regarding the neighboring cellacquired in advance (S1960).

The UE acquires the system information from the neighboring cell whenthere is no system information of the neighboring cell obtained inadvance, to be reported to the serving cell (S1930). The UE accesses theneighboring cell by temporally leaving the serving cell in order toacquire the system information of the neighboring cell. The UE mayacquire the system information of the neighboring cell through abroadcast channel by accessing the neighboring cell.

The UE reports the system information acquired by accessing theneighboring cell to the serving cell (S1940).

FIG. 20 is a flowchart illustrating one example of a method forreporting system information according to an embodiment of the presentinvention. It is assumed that the UE has already had system informationof neighboring cell A and system information of neighboring cell B to bereported.

Referring to FIG. 20, the UE receives a system information reportingrequest to request reporting the system information of neighboring cellA from the serving cell (S2010). The system information reportingrequest includes a ready-acquired system information report indicatorindicating that the UE may report the system information of neighboringcell A which is acquired in advance.

The UE receives the system information reporting request from theserving cell and verifies that it is allowed to report the systeminformation of neighboring cell A which is acquired in advance. Inresponse thereto, the UE reports to the serving cell the systeminformation of neighboring cell A which is acquired in advance (S2020).

The UE receives a system information reporting request to requestreporting the system information of neighboring cell B from the servingcell (S2030). The system information reporting request may include aready-acquired system information report indicator indicating thatreporting the system information of neighboring cell which the UEobtains in advance is not allowed or the system information reportingrequest may not include a ready-acquired system information reportindicator.

The UE receives the system information reporting request from theserving cell and verifies that it is not allowed to report the systeminformation of neighboring cell B which is acquired in advance. The UEacquires the system information by accessing neighboring cell B (S2040).

The UE acquires the system information of neighboring cell B andthereafter, reports the acquired system information to the serving cell(S2050).

The embodiments regarding the system information reporting methods arecombined with each other to be implemented with reference to FIGS. 17 to20. That is, the UE may determine whether to report the systeminformation by being indicated whether reporting the system informationwhich is acquired in advance is allowed from the serving cell. Further,the UE may encapsulate and report the control information regarding thecorresponding system information, in reporting specific systeminformation to the serving cell.

FIG. 21 is a diagram illustrating another example of the method forreporting system information according to an embodiment of the presentinvention. It is assumed that the UE has already had the systeminformation of neighboring cell A and the system information ofneighboring cell B. It is assumed that the UE does not have systeminformation of neighboring cell C.

Referring to FIG. 21, the UE receives a system information reportingrequest to request reporting the system information of neighboring cellA from the serving cell (S2110). The system information reportingrequest includes a ready-acquired system information report indicatorindicating that the UE may report the system information of neighboringcell A which is acquired in advance.

The UE receives the system information reporting request from theserving cell and verifies that it is allowed to report the systeminformation of neighboring cell A which is acquired in advance. Inresponse thereto, the UE reports to the serving cell the systeminformation of neighboring cell A which is acquired in advance (S2120).The UE transmits to the serving cell the control information regardingthe system information together in reporting the system information ofcell A. The control information may include an indicator indicating thatthe system information is the system information which is acquired inadvance before receiving a request for reporting the system informationof neighboring cell A. The control information may include an indicatorindicating the time when the system information is acquired.

The UE receives a system information reporting request to requestreporting the system information of neighboring cell B from the servingcell (S2130). The system information reporting request may include aready-acquired system information report indicator indicating that theUE may report the system information of neighboring cell B which isacquired in advance is not allowed. Alternatively, the systeminformation reporting request may not include a separate ready-acquiredsystem information report indicator.

The UE receives the system information reporting request from theserving cell and verifies that it is not allowed to report the systeminformation of neighboring cell B which is acquired in advance. The UEacquires the system information by accessing neighboring cell B (S2140).

The UE obtains the system information of neighboring cell B andthereafter, reports the acquired system information to the serving cell(S2150). The UE transmits to the serving cell the control informationregarding the system information together in reporting the systeminformation of cell B. In this case, the control information may includean indicator indicating that the system information is newly acquiredafter receiving a request for reporting the system information ofneighboring cell B. Alternatively, the control information may not beincluded. The serving cell may determine that the corresponding systeminformation is system information which is acquired after the systeminformation reporting request when separate control information is notincluded.

The UE receives a system information reporting request to requestreporting the system information of neighboring cell C from the servingcell (S2160). The system information reporting request includes aready-acquired system information report indicator indicating that theUE may report the system information of neighboring cell C which isacquired in advance.

The UE receives the system information reporting request from theserving cell and verifies that it is allowed to report the systeminformation of neighboring cell C which is acquired in advance. However,since the UE does not have the system information of neighboring cell C,the UE acquires the system information by accessing neighboring cell C(S2170).

The UE acquires the system information of neighboring cell C andthereafter, reports the acquired system information to the serving cell(S2180). The UE may transmit to the serving cell the control informationregarding the system information together in reporting the systeminformation of cell C. In this case, the control information mayindicate that the system information is newly acquired after receiving arequest for reporting the system information of neighboring cell C.Alternatively, the control information may not be included. The servingcell may determine that the corresponding system information is systeminformation which is acquired after the system information reportingrequest when separate control information is not included.

In the embodiments by referring to FIGS. 17 to 21, the systeminformation reporting request may be transmitted to the UE through ameasurement setting message. Further, a system information report may betransmitted to the UE through a measurement reporting message.

In the embodiment of the system information reporting method, the systeminformation which the UE reports to the serving cell may includeinformation described below.

When a cell associated with the system information is a cell thatsupports a CSG, the reported system information may include CSGassociated information such as a CSG ID and a CSG indicator of the cell.

When the cell associated with the system information is a cell thatsupports an MBMS, the reported system information may include MBMSassociated information such as MBMS information, MBMS configurationinformation, MBMS scheduling information, MBMS providing frequencyinformation, and/or MBSFN subframe information of the cell.

When the cell associated with the system information is a cell in whichthe measurement resource restriction is configured, the reported systeminformation may include ABS pattern information of the cell,low-interference subframe pattern information, or low-interference radioresource associated information such as a limited measurement pattern.

The reported system information may include access restrictionassociated information such as an access class barring parameter.

The reported system information may be frequency band information of oneor more uplinks associated with a downlink of the specific cell.

In the embodiments of the present invention described with reference toFIGS. 17 to 21, when the serving cell requests reporting the systeminformation of the neighboring cell, the serving cell may transfer tothe UE a system information indicator indicating that specificinformation will be transported in the system information of theneighboring cell. The system information indicator may be implemented insuch a manner that one system information indicator indicates one ormore types of information to request reporting the correspondinginformation. The system information indicator may be implemented in sucha manner that one indicator indicates a specific type of information torequest reporting one or more specific types of information throughtransmitting one or more system information indicators.

The system information indicator is included in a measurementconfiguration to be transmitted, and may be transmitted together withthe system information reporting request. The system information reportindicator may be included in a measurement object configuration and/or ameasurement report configuration. The system information which isrequested to be reported may be at least one of CSG associatedinformation, MBMS associated information, low-interference radioresource associated information, access restriction associatedinformation, and frequency band information of one or more uplinksassociated with a downlink of a specific cell.

In the embodiments of the present invention described in detail withreference to FIGS. 17 to 21, the UE may transmit to the serving cellspecific information judged/processed based on the corresponding systeminformation in reporting to the serving cell system the systeminformation which is acquired in advance and/or system information whichis newly acquired after the system information reporting request.

The specific information may include information indicating whether a UEassociated with the corresponding neighboring cell is a CSG member.

The specific information may include information indicating whether theUE may access the corresponding neighboring cell.

The specific information may include information indicating whether toreceive a specific service desired by the UE in the correspondingneighboring cell. As one example, the specific information may includeinformation indicating whether the UE may receive a service for MBMSinformation in the cell.

The specific information may be information indicating whether the UEmay be subjected to a specific radio resource configuration in thecorresponding neighboring cell. For example, the specific informationmay be information indicating whether the UE may camp on in the cell.The specific information may be information indicating whether the cellis a suitable cell for the UE. The specific information may beinformation indicating whether the cell is a cell used as the servingcell through carrier aggregation or system information required toconfigure the cell as the serving cell through the carrier aggregation.

The specific information may information representing whether thecorresponding neighboring cell is a cell which the UE may use as anadditional serving cell (Pcell or Scell).

Through the method for reporting system information described in detailwith reference to FIGS. 17 to 21, a time used for a UE to report systeminformation of a neighboring cell to a serving cell can be decreased.Therefore, a handover delay of a handover procedure requiring systeminformation of a target cell can be decreased. Further, a procedure inwhich the UE unnecessarily receives the system information of theneighboring cell is skipped, and as a result, a time when the servingcell loses controllability of the UE can be decreased.

FIG. 22 is a block diagram illustrating a wireless apparatus which maybe implemented by the embodiment of the present invention. A UE and/or abase station that performs the system information reporting methodaccording to the embodiment of FIGS. 17 and 21 may be implemented by theapparatus.

A wireless apparatus 2200 includes a processor 2210, a memory 2220, anda radio frequency unit (RF unit) 2230. The processor 2210 implements afunction, a process, and/or a method which are proposed. The processor2210 may be configured to report the system information of theneighboring cell to the serving cell in response to the systeminformation reporting request. The processor 2210 may be configured todetermined whether reporting the system information which is acquired inadvance is allowed. The processor 2210 may be configured to report thecorresponding system information to the serving cell when reporting thesystem information which is obtained in advance is allowed and thesystem information which is acquired in advance exists. The processor2210 may be configured to transmit the control information indicatingwhether the corresponding system information is the system informationwhich is acquired in advance together in reporting the systeminformation to the serving cell. The processor 2210 may be configured toimplement the embodiment of the present invention associated with thesystem information reporting method described in detail with referenceto FIGS. 17 and 21.

The RF unit 2230 is connected with the processor 2210 to transmit and/orreceive a radio signal.

The processor 2210 may include an application-specific integratedcircuit (ASIC), another chip set, a logic circuit and/or a dataprocessing apparatus. The memory 2220 may include a read-only memory(ROM), a random access memory (RAM), a flash memory, a memory card, astorage medium, and/or another storage device. The RF unit 2230 mayinclude a baseband circuit for processing the radio signal. When theembodiment is implemented by software, the aforementioned technique maybe implemented by a module (a process, a function, and the like) thatperforms the aforementioned function. The module may be stored in thememory 2220 and executed by the processor 2210. The memory 2220 may beprovided inside or outside the processor 2210 and connected with theprocessor 2210 by various well-known means.

In the aforementioned exemplary system, methods have been describedbased on flowcharts as a series of steps or blocks, but the methods arenot limited to the order of the steps of the present invention and anystep may occur in a step or an order different from or simultaneously asthe aforementioned step or order. Further, it can be appreciated bythose skilled in the art that steps shown in the flowcharts are notexclusive and other steps may be included or one or more steps do notinfluence the scope of the present invention and may be deleted.

What is claimed is:
 1. A method for reporting system information by a UE in a wireless communication system, the method comprising: receiving a system information reporting request of a neighboring cell from a serving cell; determining whether to report to the serving cell system information of the neighboring cell acquired in advance; and reporting to the serving cell the system information of the neighboring acquired in advance when it is determined to report; wherein the system information of the neighboring cell acquired in advance is system information of the neighboring cell which is acquired before receiving the system information reporting request.
 2. The method of claim 1, wherein the step of determining whether to report the system information of the neighboring cell acquired in advance includes, determining to report to the serving cell the system information of the neighboring cell acquired in advance, when the UE has the system information of the neighboring cell acquired in advance.
 3. The method of claim 2, further comprising: transmitting to the serving cell control information regarding the system information of the neighboring cell acquired in advance together with the system information of the neighboring cell acquired in advance.
 4. The method of claim 3, wherein the control information includes an indicator indicating that the system information of the neighboring cell acquired in advance is the system information of the neighboring cell acquired before receiving a system information reporting request message.
 5. The method of claim 4, wherein the control information further includes an indicator indicating the time when the system information of the neighboring cell acquired in advance is acquired.
 6. The method of claim 1, further comprising: receiving from the serving cell a ready-acquired system information report indicator indicating whether reporting the system information of the neighboring cell acquired in advance is allowed.
 7. The method of claim 6, wherein the step of determining whether to report to the serving cell the system information of the neighboring cell acquired in advance includes, determining to report to the serving cell the system information of the neighboring cell acquired in advance, if the ready-acquired system information report indicator indicates that the reporting the system information is allowed and the UE has the system information of the neighboring cell acquired in advance.
 8. The method of claim 7, further comprising: transmitting to the serving cell control information regarding the system information of the neighboring cell acquired in advance together with the system information of the neighboring cell acquired in advance.
 9. The method of claim 8, wherein the control information further includes an indicator indicating the time when the system information of the neighboring cell acquired in advance is acquired.
 10. The method of claim 1, further comprising: when it is determined not to report the system information, acquiring the system information from the neighboring cell; and transmitting the acquired system information to the serving cell.
 11. A UE that operates in a wireless communication system, the UE comprising: a radio frequency (RF) unit transmitting or receiving a radio signal; and a processor operably coupled to the RF unit, wherein the processor is configured for: receiving a system information reporting request of a neighboring cell from a serving cell, determining whether to report to the serving cell system information of the neighboring cell acquired in advance, and reporting to the serving cell the system information of the neighboring acquired in advance when it is determined to report, wherein the system information of the neighboring cell acquired in advance is system information of the neighboring cell which is acquired before receiving the system information reporting request.
 12. The UE of claim 11, wherein the determining whether to report the system information of the neighboring cell acquired in advance includes, determining to report to the serving cell the system information of the neighboring cell acquired in advance, when the UE has the system information of the neighboring cell acquired in advance.
 13. The UE of claim 12, wherein the processor is further configured for, transmitting to the serving cell control information regarding the system information of the neighboring cell acquired in advance together with the system information of the neighboring cell acquired in advance.
 14. The UE of claim 13, wherein the control information includes an indicator indicating that the system information of the neighboring cell acquired in advance is the system information of the neighboring cell acquired before receiving a system information reporting request message.
 15. The UE of claim 14, wherein the control information further includes an indicator indicating the time when the system information of the neighboring cell acquired in advance is acquired.
 16. The UE of claim 11, wherein the processor is further configured for: receiving from the serving cell a ready-acquired system information report indicator indicating whether reporting the system information of the neighboring cell acquired in advance is allowed.
 17. The UE of claim 16, wherein the determining whether to report to the serving cell the system information of the neighboring cell acquired in advance includes, determining to report to the serving cell the system information of the neighboring cell acquired in advance, if the ready-acquired system information report indicator indicates that the reporting the system information is allowed and the UE has the system information of the neighboring cell acquired in advance.
 18. The UE of claim 17, wherein the processor is further configured for, transmitting to the serving cell control information regarding the system information of the neighboring cell acquired in advance together with the system information of the neighboring cell acquired in advance.
 19. The UE of claim 18, wherein the control information further includes an indicator indicating the time when the system information of the neighboring cell acquired in advance is acquired.
 20. The UE of claim 11, wherein the processor is further configured for: when it is determined not to report the system information, acquiring the system information from the neighboring cell; and transmitting the acquired system information to the serving cell. 